1. Field of the Invention
The present invention relates to a disposable microwave reactive cooking, crisping, and browning package for foods which produces a thermal heating effect when exposed to microwave energy and which contains aperture means to allow microwave energy to dielectrically heat the center of food products contained therein.
2. Background Art
The heating and cooking of food products with microwave energy has now become extremely popular. As manufacturers of microwaveable foods attempt to meet the public's demand for additional varieties of foods which can be prepared in a microwave oven, they have experienced problems associated with enabling the product to be cooked in a microwave oven without resulting in areas which are either overcooked or undercooked. It is also desired that the cooked product possess a degree of browning or crispness which such foods normally have when cooked in a conventional oven.
Various forms of specialized packages have been developed which are designed to achieve microwave browning of foods cooked therein. These packages contain a reactive film or element which converts microwave energy into thermal energy and produces browning and crisping of an item of food situated adjacent said heating element. In some cases the food is disposed within an outer package body that is used for shipping and storage as well as for heating of the food product. In other cases, the food is disposed on a tray-like member that is situated within an outer package body for shipping and storage, but is removed or rearranged relative to the outer package body when the food item is to be heated.
One type of disposable package that is used for both shipping and storage as well as heating of items of food is represented by Brastad U.S. Pat. No. 4,267,420 and Bradtad et al., U.S. Pat. No. 4,230,924. In these patents, flexible and semi-rigid sheets of microwave interactive materials are wrapped closely about individual items of food so that when the package is exposed to microwave energy, at least a portion of the microwave energy impinging the package will be converted into heat for browning the surface of the food. However, such packages have been found to pose problems with various types of food which give off heat, grease, or vapor. Furthermore, some irregularly shaped foods may be difficult to wrap and contain without unacceptable bunching of the sheet material. Uneven heating, browning, and cooking of the food has also been experienced.
U.S. patent application No. 79,420, filed July 30, 1987, discloses a microwave browning and crisping package and method of microwave heating of food wherein a paperboard container has a microwave interactive layer affixed over one surface of the container, the inner peripheral surface defining a space for receiving a food product with top, bottom and side surfaces of the food product being in heat transfer relationship with respect to the microwave interactive layer. In use, a food item and sleeve are removed form the package body, the sleeve erected and the food item inserted therein, after which the food in the sleeve is placed in a microwave oven and heated.
These packages produced excellent cooking, crisping and browning results with low density foods. With frozen high density foods, however, the outer surface of the food browned and crisped while the center of the product remained uncooked. Products such as chimichungas and burritos could not be evenly cooked and browned in these packages. At the end of the cook cycle, a uniform temperature range of 160.degree.-180.degree. F. throughout the entire food product is the desired result.